Plasma processing apparatus

ABSTRACT

A plasma processing method for processing a sample by reducing a pressure within a processing chamber, including mounting the sample on a sample holder disposed in the processing chamber, and processing using a plasma generated in the processing chamber above the sample holder while supplying a gas for heat transfer to a space between a surface of the sample holder having the sample mounted thereon and a rear surface of the sample. The sample holder has a plurality of substantially ring-shaped depressed portions at the surface where the sample is mounted. A pressure in a space between the depressed portions arranged at a central portion of the sample holder with respect to outer circumferential portion and the sample is set to be lower than a pressure in a space between the depressed portions at the outer circumferential portion and the sample.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation application of application Ser. No.10/655,046, filed Sep. 5, 2003, which is related to U.S. patentapplication Ser. No. 11/002,265, now U.S. Pat. No. 7,303,998, thecontents of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to a plasma processing apparatus forprocessing a sample, such as a semiconductor substrate, placed on asample holder in a processing vessel by using a plasma generated in theprocessing vessel. More particularly, it relates to a plasma processingapparatus having a sample holder for processing a sample, whileadjusting the temperature of the sample.

BACKGROUND OF THE INVENTION

When the sample is processed by using the plasma formed in theprocessing vessel as described above, such factors as a temperaturedistribution in a direction across the sample holder which carries thesample placed thereon during the processing, the density distribution ofthe plasma, and the distribution of reaction products decreaseuniformity of processing across the surface of the sample, whichpresents a problem. As conventional means for solving the problem, atechnology for controlling the temperature distribution across thesurface of the sample holder and thereby adjusting the temperaturedistribution across the surface of the sample such that the processingis performed uniformly has been proposed.

across the sample holder and thereby render the temperature of thesample uniform (Prior Art Technology 1)

There has also been known another conventional technology disclosed inJapanese Patent Publication No. 2680338, which locally varies thepressure of a gas supplied to the back surface of the sample and therebyrenders the temperature of the sample uniform (Prior Art Technology 2).

Although each of the foregoing prior-art technologies has examined astructure for controlling the temperature distribution across thesurface of the sample, they have the following problems.

Since the prior art technology 1 requires a long time from the time therefrigerant temperature is changed until the sample temperature ischanged and stabilized, it presents a problem when a plurality ofdifferent processes are performed individually on a per step basis withrespect to a single wafer on a single sample holder. If each of theprocesses is not initiated until the temperature is stabilized, the timeduring which the processes are not performed increases so that theoverall processing efficiency lowers. If each of the processes isinitiated by the time the temperature is not stabilized, on the otherhand, another problem is encountered that the process cannot beperformed with high precision.

In addition, the prior art technology 1 has not considered the mutualthermal influence between the portion of the sample closer to the centerthereof and the portion of the sample closer to the outer peripherythereof even in the case of performing a process which requires a largedifference between the respective temperature values of the portioncloser to the center and the portion closer to the outer periphery.Consequently, the temperature varies gradually so that a desiredtemperature distribution is not provided.

The prior art technology 2 adjusts heat transfer between the sample andthe sample holder by varying the pressure of a gas for heat transfersupplied to the back surface of the sample under processing at desiredpositions on the back side of the sample and thereby suppressesfluctuations in temperature across the surface of the sample in ashorter period of time. However, since it is impossible to adjust thetemperature only when heat is inputted from the plasma to the wafer, apredetermined temperature distribution cannot be obtained if heatsupplied from a stably formed plasma and from a member in the processingvessel under the influence of the plasma varies greatly till it reachesa normal state and if the processing time is short. In the case ofperforming a process which requires a large difference between therespective temperatures of the portion of the sample closer to thecenter thereof and the portion of the sample closer to the outerperiphery thereof, if the amount of heat from the plasma is small, thetemperature distribution that can be provided is limited so that it isdifficult to produce a large temperature difference.

It is therefore an object of the present invention to provide a plasmaprocessing apparatus capable of adjusting the temperature of a wafer ina wide range and processing a sample to be processed with highprecision.

Another object of the present invention is to provide a plasmaprocessing apparatus which allows a desired temperature distribution tobe realized within a wafer in a shorter period of time and therebyperforms processing with higher efficiency.

SUMMARY OF THE INVENTION

The foregoing objects are attained by a plasma processing apparatus forprocessing a sample to be processed with a plasma generated by using agas, the apparatus comprising: a processing chamber having an innerspace reduced in pressure; a sample holder on which the sample isplaced, the sample holder being disposed in the processing chamber; anda plurality of openings through which the gas is introduced into theprocessing chamber, the plurality of openings being located above thesample holder, wherein the sample holder on which the sample is placedhas: ring-shaped projecting portions disposed concentrically on asurface of the sample holder to have respective surfaces thereof incontact with a surface of the sample and partition a space between thesurface of the sample and the surface of the sample holder into aplurality of regions; a first opening located in a first region, whichis the circumferentially outermost one of the plurality of regions, tointroduce a gas for heat transfer therethrough; and a second openinglocated in a second region, which is internal of the circumferentiallyoutermost region, to allow the gas in the region to flow outtherethrough.

The foregoing objects are also attained by a plasma processing apparatusfor processing a sample to be processed with a plasma generated by usinga gas, the apparatus comprising: a processing chamber having an innerspace reduced in pressure; a sample holder on which the sample isplaced, the sample holder being disposed in the processing chamber; anda plurality of openings through which the gas is introduced into theprocessing chamber, the plurality of openings being located above thesample holder, wherein the sample holder on which the sample is placedhas: a plurality of ring-shaped depressed portions over which the sampleis placed, the plurality of ring-shaped depressed portions beingdisposed substantially concentrically in a surface of the sample holder;a first opening located in a first depressed portion, which is thecircumferentially outermost one of the plurality of ring-shapeddepressed portions, to introduce a gas for heat transfer therethrough;and a second opening located in a second depressed portion, which isinternal of the circumferentially outermost depressed portion, to allowthe gas in the depressed portion to flow out therethrough.

The foregoing objects are also attained by the constitution in which thenumber of the regions resulting from the partitioning is 3 or more andby the constitution in which the second region is substantiallyevacuated.

The foregoing objects are also attained by the constitution in which thenumber of the depressed portions is 2 or more and by the constitution inwhich the second depressed portion is substantially evacuated.

The foregoing objects are also attained by the plasma processingapparatus further comprising: a plurality of paths each extendingthrough an inside of the sample holder, the plurality of paths beingdisposed in inner (or central) portions and outer peripheral portions ofinside of the sample holder, respectively, to allow refrigerantsadjusted to different temperatures to flow therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a structure of respectivecirculation paths for a gas and a refrigerant supplied to a sampleholder shown in FIG. 5, according to a first embodiment of the presentinvention;

FIG. 2 is a top view showing the configuration of the surface of thesample holder shown in FIG. 5 on which a sample is placed;

FIG. 3 is a vertical cross-sectional view schematically showing astructure for performing electrostatic adsorption on the sample holdershown in FIG. 5;

FIG. 4 is a top view schematically showing the structure of a plasmaprocessing apparatus having a processing chamber 50 shown in FIG. 6;

FIG. 5 is a vertical cross-sectional view schematically showing undermagnification the structure of a sample holder used in the plasmaprocessing apparatus shown in FIG. 6;

FIG. 6 is a vertical cross-sectional view schematically showing thestructure of a processing chamber in a plasma processing apparatusaccording to a first embodiment of the present invention;

FIG. 7 is a graph showing the distribution of the post-processingconfigurations of samples;

FIG. 8 is a graph showing a relationship between the post-processingconfiguration of a sample, each of desired temperature of a sampleholder and a position on the sample relative to the center thereof,according to the embodiment of the present invention;

FIG. 9 is a graph showing the transition of the temperatures of aplurality of samples when the processing of the samples are performedcontinuously;

FIG. 10 is a graph showing the distribution of the temperatures ofsamples obtained according to the embodiment shown in FIG. 5 and thedistribution of the temperatures of samples obtained by using the priorart technology;

FIG. 11 is a graph showing the time-varying pressure of a heat transfergas and the time-varying temperature of a sample in a process performedaccording to the embodiment shown in FIG. 5;

FIG. 12 is a graph showing the time-varying pressure of the heattransfer gas and the time-varying temperature of a sample in the processperformed according to the embodiment shown in FIG. 5; and

FIG. 13 is a flow chart illustrating the flow of the process shown inFIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 2, 5, and 6 show a first embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view schematically showing astructure of a processing chamber in a plasma processing apparatusaccording to the first embodiment. FIG. 5 is a vertical cross-sectionalview schematically showing under magnification a structure of a sampleholder used in the plasma processing apparatus shown in FIG. 6. FIG. 1is a diagram schematically showing a structure of respective circulationpaths for a gas and a refrigerant supplied to the sample holder shown inFIG. 5. FIG. 2 is a top view showing the configuration of the surface ofthe sample holder on which a sample is placed.

In FIG. 6, an overall processing chamber 200 has a stage 51 including asample holder 100 on which a sample to be processed 8 is placed inside aprocessing chamber 50. In the processing chamber 50, a processing gas issupplied from a processing gas inlet port 55 formed in the wall of theprocessing chamber 50 into an upper portion of the processing chamber 50located above a plate-like member 57 disposed over the sample 8. The gasfor processing is supplied dispersively from a plurality of throughholes 58 opened in the plate-like member (hereinafter referred to as thedispersion plate) 57 into the processing chamber 50 to reach the sample8 from thereabove.

An electromagnetic wave source 52 emits an electromagnetic wave to thegas supplied into the processing chamber 50 to generate a plasma 53. Theelectromagnetic wave from the electromagnetic wave source 52 propagatesa waveguide tube to be emitted into the processing chamber. In theembodiment shown in the drawing, the electromagnetic wave source 52emits a microwave or an electromagnetic wave in the UHF band. Threecoils 56 are disposed around a space inside the processing chamber 50located above the sample holder 100 in which the plasma 53 is formed.The distribution of the plasma density in the processing chamber isadjusted with a magnetic field supplied from the coils 56 into thespace.

Such electromagnetic wave emitting means and magnetic field supplyingmeans bring the processing gas supplied into the processing chamber 50into a high energy state so that the plasma 53 is formed in the spacelocated above the sample 8 and diffused in the processing chamber 50enclosed by the sidewalls thereof. The sample 8 is processed through thereaction between ions and high energy particles in the plasma 53 thusformed and the surface of the sample 8. Products formed through thereactions of the sample 8, the dispersion plate 57, and the members ofthe sidewalls of the processing chamber 50 with the particles in theplasma 53 during the processing of the sample 8 are exhausted, togetherwith the particles in the plasma 53 which have not contributed to thereactions or the processing of the sample 8, through an exhaust port 54located below the stage 51 or the sample holder 100 by the operation ofa vacuum pump (not shown) coupled to the exhaust port 54.

In the sample holder 100, a plurality of passages for the flow of arefrigerant for the adjustment of the temperature of the sample holder100 are disposed. There are also disposed a plurality of openings fromwhich a gas for effecting heat transfer between the back surface of thesample 8, i.e., the surface which comes in contact with the sampleholder 100 and the surface of the sample holder 100 and a plurality ofgas passages connecting to the openings to allow the gas for heattransfer to flow therethrough.

FIG. 4 shows the embodiment of the plasma processing apparatus havingthe processing chamber 50 shown in FIG. 6. A plasma processing apparatus400 shown in the embodiment is broadly divided into two parts. In theupper part of the drawing, a processing block in which the processingchamber 50 is provided and processing is performed is disposed, while anatmospheric block which transports the sample under a substantiallyatmospheric pressure between itself and the processing block is disposedin the lower part of the drawing.

A plurality of cassettes 27 containing therein the sample 8 and a dummywafer used for cleaning or the like are mounted in the atmosphericblock. The atmospheric block transports the sample 8 and the dummy waferbetween the cassettes 27 and the processing block, which will bedescribed later, by using a robot arm for transportation (not shown).

In the processing block, there are disposed units 23 and 25 forprocessing, a unit 24 for transportation capable of sealing the sample 8and transporting it under a reduced pressure, and lock chambers 26 and28 in which the pre-processing or post-processing sample 8 is placedunder a pressure reduced to a level equal to the pressure in the unit 24for transportation or increased to a substantially atmospheric pressureto be fed into the processing block and retrieved from the atmosphericblock. In the present embodiment, one of the lock chambers 26 and 28 maybe dedicated to the feeding of the sample 8 into the processing block(for loading) and the other of the lock chambers 26 and 28 may bededicated to the retrieval of the sample 8 (for unloading) from theprocessing block or, if necessary, each of the lock chambers 26 and 28may be used for both loading and unloading purposes.

Each of the processing units 23 and 25 comprises the processing chamber50 and includes a plurality of units. In particular, the processingchamber of the unit 23 is for an etching process. The processing chamberof the unit 25 is for an ashing process. Each of the processing units 23and 25 is broadly divided into upper and lower parts and has aprocessing chamber portion containing the processing chamber 50 and bedportions 401, 402, 403, and 404 containing utilities needed by theprocessing chamber portion, such as a power source, reserving portionsfor the refrigerant and gas, and a pump, which are disposed under theprocessing chamber portion. These processing units have the processingchamber portions removably attached to the transportation unit 24 andalso have the bed portions 401 to 404 removably attached to the mainbody 400 of the apparatus. The placements and types of the units arechangeable depending on the required specifications, while theoperations of attaching and detaching the units can be performed in atime shorter than in the conventional apparatus. By reducing thenon-operating time of the apparatus resulting from these operations, theoperating efficiency of the apparatus can be improved.

In the foregoing processing units, unit control devices 405, 406, 407,and 408 for adjusting the respective processing operations are disposed.A typical one of these unit control devices has a microcomputer andtransmits a signal for directing a sensor to output or operate betweenitself and the processing unit. A main control device 409 for monitoringand adjusting the overall operation of the main body 400 of theapparatus is connected to each of the unit control devices 405 to 408with or without wires to similarly transmit a signal for instructing thesensor to output or operate such that the operations of the processingunits are monitored and adjusted via the unit control devices 405 to408. It will easily be appreciated that control devices for adjustingthe operations of the atmospheric block, the transportation unit 24, andthe lock chamber 26 and 28 may also be provided such that they areconnected to the main control unit 409 to be monitored and adjustedthereby in the same manner as described above.

FIG. 5 is a vertical cross-sectional view showing in greater detail thestructure of the sample holder 100 shown in FIG. 6. In the drawing, afirst refrigerant flow path 1 is disposed closer to the center of thesample holder 100, while a second refrigerant flow path 2 is disposedcloser to the outer periphery thereof. These refrigerant flow paths 1and 2 have been disposed to adjust the temperature of the surface of agenerally cylindrical sample holder 100 on which the sample 8 is placedto provide a proper temperature distribution across the surface of thesample holder 100. In the present embodiment, the sample 8 is asemiconductor substrate having a generally disk-shaped configuration. Tosuppress differences in surface configuration resulting from the processperformed with respect to the surface of the sample 8 and in the degreeto which the surface is processed, each of the refrigerant flow paths 1and 2 is disposed in an arcuate configuration to allow the setting of aplurality of desired temperatures in the radial directions of the sample8 or the sample holder 100 and the setting of the substantially sametemperature in the circumferential direction thereof. For example, eachof the refrigerant flow paths 1 and 2 has a helical or circumferentialconfiguration.

In the present embodiment, the first refrigerant flow path 1 is providedwith an opening through which a refrigerant that has flown from thesupply side of a temperature adjuster 4 using a freezing cycle, a heatexchanger, or the like through a specified passage flows in. The otherend of the refrigerant flow path 1 opposite to the inlet openingrelative to the center of the sample holder 100 is provided with anoutlet opening through which the refrigerant that has flown through therefrigerant flow path 1 flows out. From the outlet opening, therefrigerant flows through a return path to the recovery side of thetemperature adjuster 4. Likewise, the second refrigerant flow path 2 isprovided with an opening through which the refrigerant that has flownfrom the supply side of a temperature adjuster 5 through a specifiedsupply path flows in. The other end of the refrigerant flow path 2opposite to the inlet opening is provided with an opening from which therefrigerant that has flown through the refrigerant flow path 2 flowsout. From the outlet opening, the refrigerant flows through a returnpath to the recovery side of the temperature adjuster 5.

Thus, the refrigerants flowing in the sample holder 100 circulatesthrough flow channels including the refrigerant flow paths 1 and 2 andthe temperature adjusters 4 and 5, respectively.

An atmospheric heat insulating layer 3 is further provided between thefirst and second refrigerant flow paths 1 and 2 for the purpose ofreducing temperature exchanges between the first and second refrigerantflow paths 1 and 2 and the respective portions of the sample holder 100having temperatures adjusted by the first and second refrigerant flowpaths 1 and 2 and thereby reducing a burden on each of the temperatureadjusters 4 and 5. In the present embodiment, the refrigerant flow path1 is provided at a position 0 to 115 mm radially apart from the centerof the sample holder 100, while the refrigerant flow path 2 is providedat a position 130 to 150 mm radially apart from the center of the sampleholder 100. The atmospheric heat insulating layer 3 is provided at aposition 115 to 130 mm radially apart from the center thereof.

The refrigerant for the first refrigerant flow path having a temperatureadjusted by the temperature adjuster 4 is introduced from the flowchannel into the first refrigerant flow path 1 through the openingdisposed therein and flows through the first refrigerant flow path 1,while performing heat exchange with the member closer to the center ofthe sample holder 100 to adjust the member to a first predeterminedtemperature. The refrigerant that has flown out of the first refrigerantflow path 1 through the outlet opening passes through the flow channelto return to the temperature adjuster 4. After it is adjusted to apredetermined temperature by the temperature adjuster 4, the refrigerantis introduced again into the first refrigerant flow path 1 via the flowchannel. The refrigerant for the second refrigerant flow path having atemperature adjusted by the temperature adjuster 5 is introduced fromthe flow channel into the second refrigerant flow path 2 through theopening disposed therein and flows through the second refrigerant flowpath 2, while performing heat exchange with the member closer to theouter periphery of the sample holder 100 to adjust the member to asecond predetermined temperature. The refrigerant that has flown out ofthe second refrigerant flow path 2 through the outlet opening passesthrough the flow channel to return to the temperature adjuster 5. Afterit is adjusted to a predetermined temperature by the temperatureadjuster 5, the refrigerant is introduced again into the secondrefrigerant flow path 2 via the flow channel.

Thus, the refrigerants introduced in the sample holder 100 circulate inthe flow channels in which they pass through the specified sections,while having the respective temperatures changed by the temperatureadjusters 4 and 5, to be introduced again into the sample holder 100.The temperature difference produced at this time between the tworefrigerants forms a temperature distribution across the surface of thesample 8.

The surface of the sample holder 100 is provided with three regionsdisposed as regions to each of which a gas, such as He, for performingheat transfer between the sample holder 8 and the sample holder 100 issupplied. In the present embodiment, heat transfer gases are suppliedvia gas supply paths 41, 42, and 43, respectively. The heat transfer gasis supplied from a heat transfer gas bottle 6, which is a reservingportion for the heat transfer gas, to a first heat transfer gas region17 via the flow path 41. The heat transfer gas is supplied from a gasbottle 7, which is a reserving portion for the heat transfer gas, to asecond heat transfer gas region 18 via the flow path 42. The heattransfer gas is supplied from the gas bottle 6 to a third heat transfergas region 19 via the flow path 43.

When viewed from above the sample holder 100, the first heat transfergas region has a generally circular configuration, while each of thesecond and third heat transfer gas regions has a generally circular orring-shaped configuration. One of the second and third heat transfer gasregions 2 and 3 is positioned inside the other to be disposed in asubstantially concentric configuration. In the present embodiment, thefirst heat transfer gas region 17 is disposed radially in a range of 0to 75 mm from the center of the sample holder 100, the second heattransfer gas region 18 is disposed radially in a range of 75 to 135 mm,and the third heat transfer gas region 19 is disposed radially in arange of 135 to 150 mm.

FIG. 2 shows the surface configuration of the sample holder 100 to whichsuch heat transfer gasses are supplied. In the drawing, three projectingportions 14, 15, and 16 each having a circumferential configurations aredisposed substantially concentrically on the surface of the sampleholder 100. Each of these projecting portions has an upper surfaceformed with an extremely small width. A film made of a dielectricmaterial formed by coating, spraying, or the like is disposed on thesurface of the projecting portion. The dielectric material is chargedwith a voltage applied to an electrode disposed in the sample holder 100to generate a pressing force under which the sample 8 is brought intocontact with the projecting portions and adsorbed thereby, which will bedescribed later.

The sample 8 placed on the sample holder 100 or the stage 51 having apredetermined temperature is adsorbed and held by static electricity.This brings the sample 8 placed above the sample holder 100 into contactwith the upper surfaces of the projecting portions 14, 15, and 16 anddefines the three regions to which the foregoing heat transfer gases aresupplied so that the space between the sample 8 and the depressionsformed in the surface of the sample holder 100 forms the foregoing heattransfer gas regions. That is, the foregoing projecting portions 14, 15,and 16 are for substantially hermetically sealing the heat transferregions 17, 18, and 19, respectively, while the surface of the sampleholder 100 serves as a member for performing substantially hermeticalsealing. Specifically, the sample 8 has the outer peripheral portionthereof adsorbed by static electricity (hereinafter referred to aselectrostatic adsorption) in such a manner that the leakage of the Hegas from the outer peripheral portion is suppressed, while the centerportion of the sample 8 is partially adsorbed in such a manner that thefloating of the center portion under the pressure of the transfer gas issuppressed.

A large number of extremely small protrusions are formed on the surfaceof the sample holder 100 to be located between the foregoing projectingportions 14, 15, and 16, though they are not depicted. These protrusionscome in contact with the back surface of the sample 8 at an extremelysmall area and thereby support the sample 8 on the surface of the sampleholder 100. In particular, the contact achieved between the protrusionsincluding the projecting portions 14, 15, and 16 and the sample 8 at anextremely small area reduces an amount of a foreign substance, such aswaste or a reaction product, which is exchanged between the surface ofthe sample holder 100 and the back side of the sample 8 to disturb theprocess and elongates a period till the apparatus halts and becomesnon-operative or reduces a non-operative period, thereby improving theoperating efficiency of the apparatus and the yield rate of the process.

FIG. 3 schematically shows a structure for performing electrostaticadsorption in the present embodiment. In the drawing, potentials ofdifferent polarities are imparted to conductive plates 20 and 21,respectively. This induces charges of different polarities across thesurface of the sample 8 to be adsorbed by the surface of the sampleholder 100 and generates an adsorbing force under static electricity ina direction which presses the sample 8 against the surface on the sampleholder 100, so that the sample 8 is held on the surface of the sampleholder 100. To remove (discharge) the static electricity which generatesthe adsorbing force, potentials of polarities opposite to those of thepotentials applied previously to the conductive plates 20 and 21 areapplied thereto.

Consequently, charges opposite to the charges induced by the adsorptionmove in such as manner that neutralization occurs therebetween andcharging is removed. As a result, the pin of a sample raising mechanismdenoted by 9 in FIG. 2 is operated upward to raise the sample 8 abovethe sample holder 100 and transported out of the processing chamber 50by the robot arm disposed in the transportation unit 24. The foregoingstructure prevents a situation in which the sample 8 remains in acharged state with residual charges and, even when the sample 8 is to beremoved from the sample holder 100, it cannot be removed for a longperiod of time due to the remaining adsorbing force acting on the sample8 or the sample is deformed and damaged, thereby allowing the process tobe performed with respect to another sample and improving the operatingefficiency of the apparatus.

FIG. 1 shows a structure for supplying the heat transfer gasses to thethree regions. In the drawing, the heat transfer gas emitted from thegas bottle 6 is introduced into the flow path 41 disposed between thegas bottle 6 and the first heat transfer gas region and connecting thegas bottle 6 and the first heat transfer gas region to each other. Afterhaving a pressure adjusted by a pressure adjusting valve 37 disposedabove the flow path 41, the heat transfer gas flows into the first heattransfer gas region 17 through an opening 12 located above the sampleholder 100 in facing relation to the first heat transfer gas region 17.

The heat transfer gas is filled in the first heat transfer region 17 andtransfers heat between the portion of the sample holder 100 closer tothe center thereof and the portion of the sample placed thereabove whichis closer to the center thereof. Thereafter, a part of the first heattransfer gas introduced into a heat transfer gas path leaks beyond theprojecting portion 14 disposed on the surface of the sample holder toflow into the second heat transfer region 18. The projecting portion 14may also be provided with a specified connection path connecting thefirst and second heat transfer regions 17 and 18 to allow easy flowingof the heat transfer gas into the region 18. Consequently, the pressureof the heat transfer gas in the first heat transfer gas region 17 isadjusted to a predetermined value, while gas introduction is performedby an adjusting valve 37 including a pressure detector attached in anintervening manner to the flow path connecting the first heat transfergas region 17 and the gas bottle 6 to each other.

Specifically, a temperature sensor 29 for sensing the temperature of thefirst heat transfer gas region 17 is provided in facing relation theretoor in the sample holder 100 in proximity to the first heat transfer gasregion 17. A pressure adjuster 32 which receives an output from thetemperature sensor 29 gives an instruction to the pressure adjustingvalve 37 in response to the output from a temperature sensor 29 andthereby drives it. If the difference between the output sensed by thetemperature sensor 29 and a predetermined value is equal to or largerthan a specified value, the pressure adjuster 32 having an arithmeticoperation unit such as a microcomputer determines an amount of requiredpressure variation by an arithmetic operation and gives an instructionto the pressure adjusting valve 37 to adjust the operation of the valve.Thus, the temperature sensed by the temperature sensor 29 is outputtedto be feedbacked to the adjustment of the operation of the pressureadjusting valve 37.

Likewise, the heat transfer gas emitted from the gas bottle 6 isintroduced into the flow path 43 disposed between the gas bottle 6 andthe third heat transfer gas region 19 and connecting the gas bottle 6and the third heat transfer gas region 19 to each other. After having apressure adjusted by a pressure adjusting valve 38 disposed above theflow path 43, the heat transfer gas flows into the third heat transfergas region 19 through an opening 13 located above the sample holder 100in facing relation to the third heat transfer gas region 19.

The heat transfer gas is filled in the third heat transfer region 19 andtransfers heat between the portion of the sample holder 100 closer tothe outer periphery thereof and the portion of the sample 8 placedthereabove which is closer to the outer periphery thereof. Thereafter, apart of the heat transfer gas introduced into the third heat transfergas region 19 leaks beyond the projecting portion 16 disposed on thesurface of the sample holder to the outside of the sample holder 100from the outer periphery thereof. Another part of the heat transfer gasintroduced into the third heat transfer gas region 19 leaks beyond theprojecting portion 15 disposed on the surface of the sample holder toflow in the second heat transfer region 18. The projecting portion 15may be provided with a specified connection path connecting the secondand third heat transfer regions 18 and 19 to allow easy flowing of theheat transfer gas into the region 18. Consequently, the pressure of theheat transfer gas in the third heat transfer gas region 19 is adjustedto a predetermined value, while gas introduction is performed by theadjusting valve 38 including a pressure detector attached in anintervening manner to the flow path connecting the third heat transfergas region 19 and the gas bottle 6 to each other.

Specifically, the temperature sensor 31 for sensing the temperature ofthe third heat transfer gas region 19 is provided in facing relationthereto or in the sample holder 100 in proximity to the third heattransfer gas region 19. The pressure adjuster 34 which receives anoutput from a temperature sensor 31 gives an instruction to the pressureadjusting valve 38 in response to the output from the temperature sensor31 and thereby drives it. If the difference between the output sensed bythe temperature sensor 31 and a predetermined value is equal to orlarger than a specified value, the pressure adjuster 34 having anarithmetic operation unit such as a microcomputer determines an amountof required pressure variation by an arithmetic operation and gives aninstruction to the pressure adjusting valve 38 to adjust the operationof the valve. Thus, the temperature sensed by the temperature sensor 31is outputted to be feedbacked to the adjustment of the operation of thepressure adjusting valve 38.

The heat transfer gas emitted from the gas bottle 7 toward the secondheat transfer region 18 is introduced into the flow path 42. Afterhaving a pressure adjusted by a pressure adjusting valve 39 disposedabove the flow path, the heat transfer gas flows into the second heattransfer gas region 18 through an opening 11 located above the sampleholder 100 in facing relation to the region. The heat transfer gas isfilled in the second heat transfer region 18 and transfers heat betweenthe portion of the sample holder 100 interposed between the first andthird heat transfer regions 17 and 19 and the portion of the sample 8placed thereabove which is closer to the outer periphery thereof. In thesecond heat transfer region 18, an opening 10 is further provided in theportion of the sample holder 100 facing the region. The gas in theregion is exhausted by the operation of an exhaust pump 150 for heattransfer gas through a flow path 44 connected to the exhaust pump 150for heat transfer gas via the opening 10 and an exhaust adjusting valve151.

In the same manner as in the case of each of the first and third heattransfer regions, the pressure of the heat transfer gas in the secondheat transfer gas region 18 is adjusted to a predetermined value, whileit is introduced into the second heat transfer region 18 by theoperations of the adjusting valve 39 including a pressure detectorattached in an intervening manner to the flow path connecting the regionand the gas bottle 7 to each other and of an exhaust valve 151. In thepresent embodiment, a temperature sensor 30 for sensing the temperatureof the second heat transfer gas region 18 is provided in facing relationthereto or in the sample holder 100 in proximity to the second heattransfer gas region 18. A pressure adjuster 34 having an arithmeticoperation unit such as a microcomputer receives an output from thetemperature sensor 30 for sensing the temperature of the region. Thepressure adjuster 38 is adjusted based on an instruction transmitted inresponse to the received output. The adjustment is performed byfeedbacking the temperature sensed and outputted by the temperaturesensor 30 to the adjustment of the operation of the pressure adjustingvalve 39 in the same manner as in the case of the pressure adjusters 32and 33. It is also possible to adjust the operation of the exhaustadjusting valve 151 based on the output from the temperature sensor 30in the same manner as in the case of the pressure adjusting valve 39.

Although only the openings 12 and 13 through which the heat transfer gasis supplied are located in the first and third heat transfer regions 17and 19 in the foregoing embodiment, each of the first and third heattransfer regions 17 and 19 may also have a flow path with an exhaustpump or an exhaust adjusting valve disposed therein in an interveningmanner and an opening for exhaust connecting to the flow path, similarlyto the second heat transfer region 18, such that the gas in the regionflows out to be exhausted, while the amount and speed of the exhaust isadjusted.

Since the foregoing structure transmits, to the sample 8, thetemperature distribution across the sample holder 100 having a memberlarge in volume and mass and a large heat capacity, the presentembodiment can realize a desired temperature distribution across thesample 8 by adjusting the temperature distribution across the sampleholder 100. By further transmitting the temperature of the surface ofthe sample 8 by differentiating the amount and speed of heat transfer inthe three or more regions which are the region of the sample 8 or thesample holder 100 closer to the center thereof, the region of the sample8 or the sample holder 100 closer to the outer periphery thereof, andthe region therebetween, a temperature distribution desired by the userof the apparatus can be achieved with higher precision.

The heat transfer gases introduced into the sample holder 100 areintroduced again into the sample holder 100 after having respectivepressures changed by the pressure adjusting valves 37, 38, and 39. Byadjusting the pressures of the three heat transfer gases, thetemperature distribution across the surface of the sample holder 100 orthe sample 8 becomes closer to a desired temperature distribution. Inthe present embodiment, the pressure of the gas in the second heattransfer gas region 18 is adjusted to be lower than the pressure of thegas in each of the first and third heat transfer regions 17 and 19 suchthat the heat is less likely to be transferred between the sample 8 andthe sample holder 100 in the surface portion of the sample 8 extendingradially in the range of 75 to 135 mm, i.e., the heat transfer issuppressed compared with that in the other heat transfer gas regions.This allows the temperature in the range to be higher than in the otherregions and thereby realizes a temperature distribution desired by theuser of the apparatus.

Each of the pressure adjusters 32, 33, and 34 is connected to thecontrol device 405 for the foregoing units with or without a wire totransmit and receive a signal for instructing the sensor to output oroperate. The operation of the sample holder 100 is monitored andadjusted by the control device 405.

In the present embodiment, the temperature distribution across thesurface of the sample 8 is derived from the distribution of thepost-processing configuration of the sample and from the relationshipbetween the post-processing configuration of the sample and therefrigerant temperature or the temperature of the sample holder, asshown in FIG. 7. Objective (desired) temperature distributions to beachieved in the present embodiment are shown in FIG. 8. In the drawing,the surface temperature of the sample 8 has a distribution such that itis substantially uniform from the center of the sample 8 to a certainradial point thereon and then lowers at positions radially external ofthe certain radial point, while forming an acute angle at the certainradial point serving as an inflection point, in direct proportion withthe magnitude of the radius.

In such a distribution of the surface temperature of the sample 8, thevalues of the temperatures are determined by the user of the apparatusin accordance with the distribution of reaction products over thesurface of the sample 8 which are generated during the plasma process. Adescription will be given to such a relation by using the graph shown inFIG. 8.

If the reaction products generated in the processing chamber 50 foretching the sample 8 are larger in amount in a region closer to thecenter of the sample 8 and gradually reduced in amount with approachtoward the outer periphery of the sample 8, the surface configuration ofthe sample 8 being etched is influenced by the amount and density ofthese reaction products. For example, variations in the amount of CDshifting across the surface of the sample do not present a distributionwhich is uniform throughout the surface due to such factors as thedistribution of the density of the generated plasma and the flow of thevacuum exhaust. In this case, the refrigerant temperature and thepressure of the heat transfer gas may be set properly in the followingmanner in accordance with the variations in the amount of CD shiftingacross the surface of the sample. Since it is considered that the sampletemperature is higher at a portion with a small mount of CD shifting andtherefore the reaction products are less likely to be adhered againthereto, an improvement can be made by adjusting the refrigeranttemperature and the pressure of the heat transfer gas to reduce thesample temperature and thereby reducing the differences in CD shiftingacross the surface of the sample.

Specifically, in a region inside the reaction chamber 50 in which thereaction products are higher in density (larger in amount), thetemperature of the sample holder 100 located thereunder is increased toincrease the surface temperature of the sample 8 and thereby suppressthe re-adhesion of the reaction products to the surface of the sample 8.In a region in which the reaction products are lower in density (smallerin amount), on the other hand, the temperature of the sample holder 100located thereunder is reduced to adjust the amount of the reactionproducts adhered to the surface of the sample 8 and thereby bring thespeed at which the whole sample is processed closer to uniformity.

Thus, the distribution of the temperature values across the sample 8 andthe distribution of the temperature values across the sample holder 100for adjusting the temperature distribution across the sample 8 aredetermined in accordance with the distribution of the density of thereaction products. In short, the temperature distribution across thesample holder 100 is determined such that the temperature is higher atthe portion thereof closer to the center and gradually lowers withapproach toward the outer periphery. FIG. 8 shows an example of thetemperature distribution.

It can be considered that the temperature distribution in anotherprocess performed with respect to a sample and influenced by theadhesion of reaction products to the sample also has the same tendencyas shown in FIG. 8. For example, the temperature inflection point islocated more internally when the speed at which the reaction productsare exhausted from the processing chamber is higher than in FIG. 8 sothat the temperature difference between the center portion and theoutermost peripheral portion is increased. Accordingly, the respectivepositions of the plurality of heat transfer regions to which the heattransfer gases are supplied are varied in the radial direction of thesample or the sample holder in accordance with the characteristic of thetemperature distribution. It will easily be understood that thetemperature distribution may vary depending on the type of the sample,the speed at which the reaction products are exhausted, or the like.Therefore, the present invention is by no means limited to thedistribution of the values and the configuration of the graph shown inFIG. 8.

A description will be given to temperature distributions implemented byusing the foregoing structure with reference to FIG. 10. In FIG. 10, thepressure in each of the first and third heat transfer gas regions 17 and19 is adjusted to, e.g., 1.5 kPa. By contrast, the pressure in thesecond heat transfer gas region 18 is approximately 0 kPa since theintensity of exhaust from the second heat transfer gas region 18 is highand the speed of exhaust is sufficiently higher than the respectivespeeds of the gases flown from the first and third heat transfer regions17 and 19 into the second heat transfer region 18 and of the gassupplied to the second heat transfer region 18 or since no gas issupplied to the region.

However, the pressure in the second heat transfer gas region 18 shouldbe varied responsively to the amount of heat supplied to the region ofthe sample 8 (heat input) located above the region. If a comparison ismade between the respective pressures when the heat input is high andwhen the heat input is low, the pressure is relatively high when theheat input is high, while the pressure is adjusted to a relatively lowlevel when the heat input is low. If the sample 8 is a semiconductorwafer and gate processing using a semiconductor etching process isperformed with respect to the wafer, the heat input is considerablylower than in the step with a high heat input such as the processing ofan insulating film, which is about 50 W to 100 W. In this case, apressure of about 0 to 0.5 kPa is sufficient for the second heattransfer gas region 18.

Thus, the heat transfer gases introduced into the sample holder 100 areintroduced again into the sample holder 100 after having respectivepressures changed by the pressure adjusting valves 37, 38, and 39. Byadjusting the individual pressures of the three heat transfer gases, thetemperature distribution across the surface of the sample holder 100 isbrought closer to a desired temperature distribution. By particularlyadjusting the pressure of the gas in the second heat transfer gas region18 to be lower than the pressure of the gas in the third heat transfergas region 19, the heat supplied to the sample in the surface portion ofthe sample extending radially in the range of 75 to 135 mm is made lesslikely to be transferred to the sample holder 100. By achieving a higherheat insulating effect than in the other heat transfer gas regions, thetemperature in the range becomes higher than in the other regions to becloser to an objective and ideal temperature distribution 101.

In the temperature distribution 103 having the two heat transferregions, which has been obtained by using the prior art technology, thepressure of the heat transfer gas in the outer circumferential heattransfer region is adjusted to be higher and the pressure in the innercircumferential heat transfer region is adjusted to be lower so that thetemperature of the sample is higher in the inner region. The temperatureat a middle point in the outer region is influenced and determined bythe pressure of the heat transfer gas and by the amount of heat suppliedto this region. At the portion 140 mm apart from the center of thesample 8, in particular, the lowest temperature is reached. Likewise,the temperature at a middle point in the region closer to the center(center portion of the sample 8) is determined by the pressure of thesupplied heat transfer gas and by the amount of heat supplied to theregion closer to the center of the sample.

According to the prior art technology, however, heat shift occursbetween the region of the wafer on the heat transfer region closer tothe center and the region of the wafer on the heat transfer regioncloser to the outer periphery so that the temperature variations in theboth regions are gradual from the center of the sample 8 to the positioncloser to the outer periphery at which the lowest temperature isreached. Compared with the objective temperature variation 100, a largedifference is produced in the vicinity of a point at a distance of 100mm from the center of the sample 8 so that a temperature lower than theobjective value is provided. In contrast to the prior art technology,the present embodiment has the second heat transfer region in which thepressure of the gas is adjusted to be lower than in each of the heattransfer regions closer to the center and closer to the outer peripheryand adjusts the temperature in the second region to be higher, asdescribed above. Consequently, the temperature variation 102 across thesample 8 according to the present embodiment brings the temperatures inthe second and third heat transfer regions closer to the objectivetemperature distribution 100 and allows more uniform processing acrossthe sample 8.

The pressures and flow rates of the heat transfer gases are adjusted byusing pressure adjusting valves such that a desired temperature isachieved at a specified position on the surface of the sample 8 byparticularly feedbacking the respective temperatures of the heattransfer regions measured by using the temperature sensors to therespective pressure adjusters for the individual regions and therebyadjusting the amount of heat transfer between the sample 8 and thesample holder 100.

Referring to FIGS. 11 to 13, a description will be given to theoperation of processing a sample according to the present embodiment.FIGS. 11 and 12 are graphs for illustrating a temperature and variationsin the pressure of the heat transfer gas in the processing of the sampleaccording to the embodiment shown in FIG. 6. FIG. 13 is a flow chartshowing the flow of the operation of the processing according to thepresent embodiment shown in FIG. 11.

In the present embodiment, the sample holder 100 is internally providedwith a plurality of refrigerant flow paths 1 and 2 that can be adjustedto different temperatures. Prior to the processing, the temperature inthe refrigerant flow paths 1 and 2 are adjusted and refrigerants areallowed to flow therethrough to adjust the temperature of the sampleholder 100 such that the temperature distribution across the surface ofthe sample holder 100 on which the sample 8 is placed provides a desiredtemperature distribution across the surface of the sample 8.

The temperature values over the sample holder 100 are determined underconsideration such that the temperature of the sample 8 has a propervalue when a plasma is generated and heat is supplied. In this case, therespective pressures in the three heat transfer gas regions between theback surface of the sample 8 and the surface of the sample holder 100 onwhich the sample is placed are selected such that the temperature of thesample holder 100 is reflected more precisely in the sample 8. In thepresent embodiment, each of the respective pressures in the three heattransfer regions 17, 18, and 19 is set to 1.5 kPa.

If the pressure in the second heat transfer gas region 18 is low priorto the processing of the sample, i.e., when no heat has been inputted, aheat insulating portion is formed thereby and a point at a radialdistance of about 75 mm, which corresponds to the terminal end of thefirst heat transfer gas region 17, becomes a temperature inflectionpoint so that the resulting temperature distribution deviates from apredetermined temperature distribution. If the pressure in the secondheat transfer gas region 18 is high, on the other hand, the temperaturedistribution across the sample holder 100 is reflected so that a pointat a radial distance of about 100 mm becomes an inflection point and theresulting temperature distribution is closer to the specified one.

After the sample 8 is placed on the sample holder 100, the processinggas is introduced into the processing chamber 50, while anelectromagnetic wave is emitted, so that the plasma 53 is formed in theprocessing chamber 50. The surface of the sample 8 is processed with theplasma 53. Simultaneously with the formation of the plasma 53, thesupply of heat from the plasma 53 to the sample 8 is started. When theformation of the plasma or the processing of the sample is started, thepresent embodiment exhausts the second heat transfer gas region 18. Thegas in the region is exhausted at a high speed through the exhaust hole10 by using the exhaust pump 150 so that the regions 18 is evacuatedrapidly and a high degree of vacuum is achieved therein. By thusbringing the second heat transfer region into a high vacuum state at theinitial stage of the processing of the sample 8, the maximum heatinsulating effect is achieved and the temperature at a position on thesample 8 at a radial distance of about 100 mm, which is located abovethe second heat transfer region, is increased so that the actualtemperature distribution is brought closer to an objective temperaturedistribution in a shortest possible time.

When the temperature in the second heat transfer region 18 reaches apredetermined temperature, the pressure therein is adjusted to a valuewhich provides the predetermined temperature distribution so that thepressure in the second heat transfer region 18 is brought into a normalstate and the predetermined temperature distribution is retained.Specifically, the pressure of the gas is adjusted this time to a highestpossible value so that a further temperature increase resulting from theheat supplied from the plasma 53 is suppressed and the temperature isprevented from becoming lower than a required level.

The pressure of the heat transfer gas which provides the second heattransfer region 18 with such a temperature is typically lower than eachof the respective heat transfer gasses in the first and third heattransfer regions located on both sides. For the purpose of implementingthe temperature distribution shown in FIG. 10, the pressure of the heattransfer gas in the third heat transfer region 19 is adjusted to behigher to provide a high heat transfer rate. In the first heat transferregion 17, the heat transfer rate is relatively lowered and the pressureof the heat transfer gas is adjusted to be lower so that the temperatureon the surface of the sample 8 is adjusted to be higher than in thethird heat transfer region.

In the second heat transfer region 18, by contrast, the pressure of theheat transfer gas is adjusted to be lower than in either of the firstand third heat transfer regions 17 and 19 so that the heat transfer rateis further reduced. Consequently, the temperature of the region of thesample 8 located above the second heat transfer region 18 is adjusted toa higher level so that the temperature distribution across the sample 8is brought closer to a desired temperature distribution, e.g., the graph100 in FIG. 10.

The flow of the operation of such pressure adjustment in the second heattransfer gas region 18 is shown in FIG. 13, while the results oftemperature distributions across the sample are shown in FIGS. 11 and12.

First, the temperature of each of the refrigerants in the sample holder100 is adjusted to a predetermined temperature (Step S1301). Next, thetemperature of the refrigerant is sensed by sensing the temperature atthe specified position on the sample holder 100 (Step S1302) andcompared with specified values (Step S1303). If the temperature ishigher than the first predetermined value (high temperature), the flowrate of the refrigerant is increased or the temperature of therefrigerant to supplied is reduced. If the temperature is lower as aresult of a comparison with a second predetermined value (lowtemperature), the flow rate of the refrigerant is reduced or thetemperature of the refrigerant to be supplied is higher (Step S1304).Thus, the temperature over the surface of the sample holder 100 on whichthe sample 8 is placed is adjusted to provide a desired temperaturedistribution.

The adjustment of the temperature over the sample holder 100 using therefrigerant can be performed either before or after the sample 8 isplaced.

Then, the heat transfer gases are supplied to the first, second, andthird heat transfer regions 17, 18, and 19 in the same manner as inSteps S1301 to 1304. By using the respective outputs from thetemperature sensors 29, 30, and 31 in the individual regions and thepressure adjusting valves 37, 38, and 39, the pressure adjusters 32, 33,and 34 adjust the respective pressures of the heat transfer gases in theindividual regions (Step S1305).

If a desired temperature distribution across the sample 8 prior toprocessing is recognized based on the outputs from the temperaturesensors 29, 30, and 31, a plasma is formed by introducing a gas and anelectromagnetic wave into the processing chamber 500 located above thesample 8 (Step S1306). If the formation of the plasma is recognized(Step S1307), the pressure adjuster 32 transmits an instruction to lowerthe pressure in the first heat transfer region 17 to the pressureadjusting valve 37, thereby reducing the opening of the valve (StepS1311). On the other hand, in order to make the pressure in the secondheat transfer region 18 lower than the first heat transfer region 17,the pressure adjuster 33 transmits an instruction to each of thepressure adjusting valves 39 and 151 and the exhaust pump 150 to adjustthe operations thereof (Step S1308). For example, the opening of thepressure adjusting valve 39 is reduced. Alternatively, the output of theexhaust pump 150 is increased and the opening of the pressure adjustingvalve 151 is increased, whereby the speed of exhaust from the exhausthole 10 is increased.

By the foregoing operation, the pressure in the second heat transferregion 18 is adjusted to be lower than the pressure in the first heattransfer region 17 and lower than the pressure in the third heattransfer region 19 so that a high vacuum state is provided. Byminimizing the heat transfer rate in the second heat transmission region18, the temperature of the region of the sample 8 located above thisregion is increased rapidly.

Next, the pressure adjuster 33 detects the temperature of the secondheat transfer region 18 upon receipt of an output from the temperaturesensor 30. If the pressure adjuster 33 senses that the temperature ishigher than a predetermined value, it gives an instruction to each ofthe pressure adjusting valves 39 and 151 and the exhaust pump 150 toadjust the pressure in the second heat transfer region 18 so that thetemperature in the region becomes closer to a desired objectivetemperature (Step S1309). For example, the pressure in the second heattransfer region 18 is increased by increasing the opening of thepressure adjusting valve 39, by reducing the opening of the pressureadjusting valve 151, or by reducing an output from the exhaust pump 150and thereby reducing the speed of exhaust from the exhaust hole 10. Inthis case also, the pressure in the second heat transfer region 18 isadjusted to be lower than the pressure of the gas in each of the firstand third heat transfer regions 17 and 19 (Step S1310).

In the mean time, the pressure of the gas in the third heat transferregion 19 is adjusted to be substantially equal. Of the three regions,the region of the sample 8 located above the third heat transfer region19 is a region at the circumferentially outermost position in which thetemperature is adjusted to a lowest level, while defining one end whichdetermines a temperature distribution across the sample 8. As shown inFIG. 8, the temperature over the sample 8 preferably has a downwardlyinclined distribution shown on the graph such that a lowest temperatureis achieved at the outer circumferential end. To implement thetemperature, the third heat transfer region is shortest in the radialdirection of the sample holder 100 or the sample 8. In the presentembodiment, the region defining the other end which determines thetemperature distribution across the sample 8 is the first heat transferregion 17. The temperature distribution across the sample holder 100 orthe sample 8 in the present embodiment is basically determined byadjusting the respective temperatures in the two regions.

The second heat transfer region 18 disposed between these regions is aportion determining the inclination of temperature variation between thetemperature of the region of the sample 8 located above the second heattransfer region 18 and each of the lowest temperature determined in theregion of the sample 8 located above the third heat transfer region 19adjacent to the second heat transfer region 18 on the outercircumferential side thereof and the temperature of the region of thesample 8 closer to the center thereof which is located above the firstheat transfer region 17 adjacent to the second heat transfer region 18on the inner circumferential side thereof. By adjusting the temperaturein the second heat transfer region 18, a temperature distribution closerto an ideal temperature distribution is implemented across the sample 8in which an inflection point for the temperature variation over thesample 8 is provided and the temperature on the surface of the sample issubstantially the same to a point closer to the center portion of thesample 8 which is at a given radial distance and the temperaturecontinues to decrease in the region radially external of the positionwith approach toward the outer periphery.

In the example shown in the foregoing embodiment, heat with which thetemperature of the second heat transfer region 18 becomes higher thanthe predetermined objective value during the processing of the sample 8is supplied from the plasma. Depending on conditions for processingusing the plasma, there are cases where, even if the processing isinitiated while relatively low heat is supplied from a plasma and thepressure in the second heat transfer region 18 is maintained at a highdegree of vacuum, the temperature in the region 18 and the temperatureof the region of the sample 8 located above the region 18 do not reachan objective temperature during the processing. FIG. 12 showstemperature variation in this case.

In this case, even when the pressure in the second heat transfer region18 is adjusted to approximately 0 KPa after the initiation ofprocessing, the temperature of the sample 8 has not reached an objectivetemperature during the processing at a position 100 mm apart from thecenter of the sample 8, which is located above the second heat transferregion 18. In this case also, the inclination of the temperaturevariation (variation with time in temperature increase) shows that therate of temperature variation to time variation is higher than in theheat transfer region 19 where the pressure of the supplied heat transfergas is not varied and that a temperature distribution closer to an idealtemperature distribution across the sample can be realized.

Since the temperature of the sample is lower than a predeterminedtemperature distribution during the initial period of processing, thetemperature at the position in the region of the sample 8 located abovethe second heat transfer region 18 is increased till it exceeds apredetermined temperature by providing a higher vacuum state andminimizing the heat transfer rate. By thus thinning the sample with athick configuration as a result of processing in a state lower than thepredetermined temperature during the initial period, i.e., in a state inwhich a larger amount of reaction products is likely to be adhered tothe sample, the sample with a final post-processing configurationequivalent to that when a predetermined temperature is obtainable in theinitial state is obtainable.

The structure provides a distribution closer to the predeterminedtemperature distribution even when the processing time is short andreduces an amount of temperature variation till the predeterminedtemperature distribution is provided.

Thus, the present embodiment allows a temperature gradient to be formedacross the sample holder so that a temperature distribution is formed asrequired across the surface of the sample.

By providing three circulation systems for the heat transfer gases andlocally providing high-speed exhausting means, high-precisiontemperature control can be performed across the surface of the sample.

Since the three refrigerant flow paths can be controlled independentlyby using the three pressure adjusters, it is possible to freely combinetemperature control, flow rate control, and the type of a refrigerant.If it is assumed that only flow rate control is performed, the type andtemperature of a refrigerant are fixed. Accordingly, the production of atemperature difference across the surface of the sample is limited andthe type of a usable process is also limited. According to the presentembodiment, however, a large temperature difference can be producedacross the surface of the sample.

When a plurality of samples 8 are to be processed continuously, thetemperature of the sample holder 100 requires a long time to reach anormal state and the temperatures of the first and second samples arelower than those of the subsequent samples as shown in FIG. 9 so thatsuch a structure is effective in eliminating the problem. Although ithas frequently been performed to add a heat input prior to theprocessing of the samples and thereby hold the temperature of the sampleholder in a normal state by using a technique such as aging, it issufficient to adjust the pressure of the heat transfer gas to be loweronly for the first and second samples.

Although the present embodiment has shown a structure using threetemperature adjusters, the concept of the present embodiment isapplicable without any alteration even to a structure using three ormore temperature adjusters. As the number of temperature adjusters isincreased, the accuracy with which the temperature profile is feedbackedis increased, which is an object of the present embodiment.

The temperature distribution across the sample holder should bedetermined depending on the distribution of reaction products formedunder the influence of the configurations, placement, and number ofrefrigerant trenches, the type of a processing gas, the pressure in theprocess, the position of an exhaust system, and the like. Hence, theplacement of the refrigerant flow paths is not limited to the foregoing.

Although the foregoing embodiments have been described by using theplasma etching apparatus as an example, the present invention is widelyapplicable to a processing apparatus in which a subject to be processed,such as a sample, is processed while being heated in an atmosphere undera reduced pressure. As examples of a processing apparatus using aplasma, there can be listed a plasma etching apparatus, a plasma CVDapparatus, a sputtering apparatus, and the like. As examples of aprocessing apparatus not using a plasma, there can be listed an ionimplantation apparatus, an MBE apparatus, a vapor deposition apparatus,a vacuum CVD apparatus, and the like.

1. A plasma processing apparatus for processing a sample with a plasmagenerated by using a processing gas, the apparatus comprising: aprocessing chamber having an inner space reduced in pressure; a sampleholder on which said sample is placed, said sample holder being disposedin said processing chamber, wherein at least one refrigerant flow pathis disposed inside said sample holder; a plurality of openings throughwhich said processing gas is introduced into said processing chamber,said plurality of openings being located above the sample holder; and anevacuating opening disposed under the sample holder through which theprocessing chamber is evacuated; wherein said sample holder includes: anelectrode disposed inside the sample holder which electrostaticallyadsorbs said sample on a surface of the sample holder, a ring-shapedprojecting partition disposed concentrically on a surface of said sampleholder to have a surface thereof in contact with a surface of saidsample and partitions a space between the surface of the sample and thesurface of the sample holder into a plurality of regions next to eachother, a plurality of second openings each of which is located in acorresponding one of said plurality of regions, to introduce a heattransfer gas for heat transfer therethrough, and a third opening locatedin a circumferentially outer region of said plurality of regions, toallow the heat transfer gas in the circumferentially outer region toflow out therethrough and exhausted, whereby said heat transfer gas ineach of said plurality of regions are adjustable in different pressurewhen said sample is electrostatically adsorbed on the surface of saidsample holder.
 2. The plasma processing apparatus of claim 1, whereinsaid circumferentially outer region is substantially evacuated throughsaid third opening.
 3. A plasma processing apparatus for processing asample with a plasma generated by using a processing gas, the apparatuscomprising: a processing chamber having an inner space reduced inpressure; a sample holder on which said sample is placed, said sampleholder being disposed in said processing chamber, wherein at least onerefrigerant flow path is disposed inside said sample holder; and aplurality of openings through which said processing gas is introducedinto said processing chamber, said plurality of openings being locatedabove the sample holder, wherein said sample holder includes: anelectrode disposed inside the sample holder which electrostaticallyadsorbs said sample on the surface of the sample holder, pluraldepressed portions over which said sample is placed, the pluraldepressed portions being disposed substantially concentrically next toeach other in a surface of the sample holder, a ring-shaped projectionpartition disposed on a surface said sample holder to have a surfacethereof in contact with a surface of said sample holder and partitionssaid plural depressed portions between the surface of the sample and thesurface of said sample holder into a plurality of regions, a pluralityof second openings each of which is located in a corresponding one ofsaid plurality of regions, to introduce a heart transfer gas for heattransfer therethrough, and a third opening located in acircumferentially outer region of said plurality of regions, to allowthe heat transfer gas in the circumferentially outer region to flow outtherethrough and exhausted, whereby said heat transfer gas in each ofsaid plurality of regions are adjustable in different pressure when saidsample is electrostatically adsorbed on a surface of said sample holder.4. The plasma processing apparatus of claim 3, wherein saidcircumferentially outer region is substantially evacuated through saidthird opening.
 5. The plasma processing apparatus of claim 1, wherein: aplurality of said refrigerant flow paths extend through inside of saidsample holder, said plurality of refrigerant flow paths being disposedin inner or central portions and other peripheral portions of inside thesample holder, respectively, to allow refrigerants adjusted to differenttemperatures to flow therethrough.
 6. The plasma processing apparatus ofclaim 3, wherein: a plurality of said refrigerant flow paths extendthrough inside of said sample holder, said plurality of refrigerant flowpaths each extending through an inside of said sample holder, saidplurality of refrigerant flow paths being disposed in inner or centralportions and other peripheral portions of inside the sample holder,respectively, to allow refrigerants adjusted to different temperaturesto flow therethrough.
 7. The plasma processing apparatus of claim 1,wherein said plurality of regions are divided into through regionsfurther comprising: a controller which adjustable a pressure of saidheat transfer gas in the respective regions.
 8. The plasma processingapparatus of claim 3, further comprising: a controller which adjustablea pressure of said heat transfer gas in the respective region.